In an existing Long Term Evolution (Long Term Evolution, LTE) communication system, a base station needs to send user equipment scheduling information by using a downlink subframe. The time-frequency resources of the downlink subframe are divided into two regions: a physical downlink control channel (Physical Downlink Control Channel, PDCCH) region and a physical downlink data channel (Physical Downlink Shared CHannel, PDSCH) region. The PDCCH region is used to transmit downlink or uplink data transmission scheduling indication signaling sent by a base station to a user equipment, including information related to data channel resource allocation, a modulation and coding scheme, and a multi-antenna transmission or hybrid automatic repeat request (Hybrid Automatic Repeat Request, HARQ) process; and the PDSCH region is used to carry specific scheduling data.
As shown in FIG. 1, in a downlink subframe, a PDSCH region and a PDCCH region employ a time division multiplexing mode. The PDCCH region (that is, the part filled with slashes in FIG. 1) occupies the first N orthogonal frequency division multiplexing (Orthogonal Frequency Division Multiplexing, OFDM) symbols of the downlink subframe, where N is dynamically variable and less than or equal to 3, and the PDSCH region occupies the remaining OFDM symbols.
Scheduling information sent by a base station for multiple user equipments may be multiplexed in the PDCCH region in a subframe. The PDCCH region corresponding to each user equipment may be composed of 1 or 2 or 4 or 8 control channel elements (Control Channel Element, CCE). Such compositions correspond respectively to different coding rates. In this way, in the PDCCH region of the downlink subframe, CCEs make up the PDCCH region of different user equipments to carry the user equipment scheduling information sent by the base station. When receiving a downlink subframe sent by the base station, a user equipment does not know which CCEs make up a PDCCH region corresponding to the user equipment. Therefore, the user equipment needs to detect the corresponding PDCCH region blindly in a common search space and a specific search space. Specifically, the user equipment detects control channels of all possible CCE combinations (that is, 1 CCE, 2 CCEs, 4 CCEs, and 8 CCEs) in the received downlink subframe until the PDCCH region corresponding to the user equipment is detected.
To provide higher spectrum efficiency and cell edge user performance, in an evolved release (Release, R) system of an LTE system, that is, in an R11 system, coordinated multi-point (CoMP) and a more flexible multiple-input multiple-output (Multiple-Input Multiple-Output, MIMO) scheduling mechanism are introduced so that a cell can serve much more user equipments concurrently. Therefore, in a downlink subframe sent by the base station, a PDCCH region with at most three OFDM symbols cannot meet requirements of the R11 system, and a new PDCCH resource needs to be defined, that is, an extended physical downlink control channel (Extended Physical Downlink Control Channel, E-PDCCH) region, which uses a part of time-frequency resources of the original PDSCH region and can be multiplexed with the PDSCH region through frequency division multiplexing or time-frequency division multiplexing.
To avoid increase of blind detection of control channels by a user equipment, an existing solution is to limit uplink and downlink scheduling information of a user equipment of the R11 system to be transmitted by a base station only within an E-PDCCH region, so that the user equipment needs only to perform blind detection of the E-PDCCH region in a common search space and a specific search space. However, in a non-evolved release (R8/9/10) system of the LTE system, if the quantity of user equipments is small, the PDCCH region is not fully occupied, but the remaining PDCCH region resources are not available to the user equipments in the R11 system, which leads to low resource utilization.